Bug 1552126 - Convert layers.componentalpha.enabled to a non-Skip pref. r=mattwoodrow

Differential Revision: https://phabricator.services.mozilla.com/D37372

--HG--
extra : moz-landing-system : lando

gfx/layers/Layers.cpp

@@ -138,8 +138,18 @@ already_AddRefed<ImageContainer> LayerManager::CreateImageContainer(
   return container.forget();
 }
 
+bool LayerManager::LayersComponentAlphaEnabled() {
+  // If MOZ_GFX_OPTIMIZE_MOBILE is defined, we force component alpha off
+  // and ignore the preference.
+#ifdef MOZ_GFX_OPTIMIZE_MOBILE
+  return false;
+#else
+  return StaticPrefs::layers_componentalpha_enabled_do_not_use_directly();
+#endif
+}
+
 bool LayerManager::AreComponentAlphaLayersEnabled() {
-  return StaticPrefs::layers_componentalpha_enabled();
+  return LayerManager::LayersComponentAlphaEnabled();
 }
 
 /*static*/

gfx/layers/Layers.h

@@ -388,6 +388,12 @@ class LayerManager : public FrameRecorder {
       const nsTArray<nsIWidget::Configuration>& aConfigurations) {}
   bool IsSnappingEffectiveTransforms() { return mSnapEffectiveTransforms; }
 
+  /**
+   * Returns true if the underlying platform can properly support layers with
+   * SurfaceMode::SURFACE_COMPONENT_ALPHA.
+   */
+  static bool LayersComponentAlphaEnabled();
+
   /**
    * Returns true if this LayerManager can properly support layers with
    * SurfaceMode::SURFACE_COMPONENT_ALPHA. LayerManagers that can't will use

gfx/layers/d3d11/CompositorD3D11.cpp

@@ -10,6 +10,7 @@
 
 #include "gfxWindowsPlatform.h"
 #include "nsIWidget.h"
+#include "Layers.h"
 #include "mozilla/gfx/D3D11Checks.h"
 #include "mozilla/gfx/DeviceManagerDx.h"
 #include "mozilla/gfx/GPUParent.h"
@@ -1050,7 +1051,7 @@ void CompositorD3D11::DrawGeometry(const Geometry& aGeometry,
       mContext->PSSetShaderResources(TexSlot::Y, 3, srViews);
     } break;
     case EffectTypes::COMPONENT_ALPHA: {
-      MOZ_ASSERT(StaticPrefs::layers_componentalpha_enabled());
+      MOZ_ASSERT(LayerManager::LayersComponentAlphaEnabled());
       MOZ_ASSERT(mAttachments->mComponentBlendState);
       EffectComponentAlpha* effectComponentAlpha =
           static_cast<EffectComponentAlpha*>(aEffectChain.mPrimaryEffect.get());

gfx/layers/d3d11/DeviceAttachmentsD3D11.cpp

@@ -9,6 +9,7 @@
 #include "mozilla/Telemetry.h"
 #include "mozilla/layers/Compositor.h"
 #include "CompositorD3D11Shaders.h"
+#include "Layers.h"
 #include "ShaderDefinitionsD3D11.h"
 
 namespace mozilla {
@@ -179,7 +180,7 @@ bool DeviceAttachmentsD3D11::Initialize() {
     return false;
   }
 
-  if (StaticPrefs::layers_componentalpha_enabled()) {
+  if (LayerManager::LayersComponentAlphaEnabled()) {
     D3D11_RENDER_TARGET_BLEND_DESC rtBlendComponent = {
         TRUE,
         D3D11_BLEND_ONE,
@@ -275,7 +276,7 @@ bool DeviceAttachmentsD3D11::CreateShaders() {
   InitPixelShader(sYCbCrShaderMask, mYCbCrShader, MaskType::Mask);
   InitPixelShader(sNV12Shader, mNV12Shader, MaskType::MaskNone);
   InitPixelShader(sNV12ShaderMask, mNV12Shader, MaskType::Mask);
-  if (StaticPrefs::layers_componentalpha_enabled()) {
+  if (LayerManager::LayersComponentAlphaEnabled()) {
     InitPixelShader(sComponentAlphaShader, mComponentAlphaShader,
                     MaskType::MaskNone);
     InitPixelShader(sComponentAlphaShaderMask, mComponentAlphaShader,

gfx/layers/opengl/CompositorOGL.cpp

@@ -1550,7 +1550,7 @@ void CompositorOGL::DrawGeometry(const Geometry& aGeometry,
       BindAndDrawGeometry(program, aGeometry);
     } break;
     case EffectTypes::COMPONENT_ALPHA: {
-      MOZ_ASSERT(StaticPrefs::layers_componentalpha_enabled());
+      MOZ_ASSERT(LayerManager::LayersComponentAlphaEnabled());
       MOZ_ASSERT(blendMode == gfx::CompositionOp::OP_OVER,
                  "Can't support blend modes with component alpha!");
       EffectComponentAlpha* effectComponentAlpha =

modules/libpref/init/StaticPrefList.h

@@ -4009,25 +4009,21 @@ VARCACHE_PREF(
   RelaxedAtomicBool, true
 )
 
-#ifdef MOZ_GFX_OPTIMIZE_MOBILE
-// If MOZ_GFX_OPTIMIZE_MOBILE is defined, we force component alpha off
-// and ignore the preference.
-VARCACHE_PREF(
-  Skip,
-  "layers.componentalpha.enabled",
-   layers_componentalpha_enabled,
-  bool, false
-)
-#else
-// If MOZ_GFX_OPTIMIZE_MOBILE is not defined, we actually take the
-// preference value, defaulting to true.
 VARCACHE_PREF(
   Once,
   "layers.componentalpha.enabled",
-   layers_componentalpha_enabled,
-  bool, true
-)
+   layers_componentalpha_enabled_do_not_use_directly,
+  bool,
+  // Nb: we ignore this pref if MOZ_GFX_OPTIMIZE_MOBILE is defined, as if this
+  // pref was always false. But we go to the effort of setting it to false so
+  // that telemetry's reporting of the pref value is more likely to reflect
+  // what the code is doing.
+#ifdef MOZ_GFX_OPTIMIZE_MOBILE
+  false
+#else
+  true
 #endif
+)
 
 VARCACHE_PREF(
   Once,